Unit 2 · Parallel and Perpendicular Lines

2.2Parallel Lines and Transversals

Quick Answer

When parallel lines are cut by a transversal: corresponding angles are congruent, alternate interior angles are congruent, alternate exterior angles are congruent, and co-interior angles are supplementary.

Essential Question

What angle relationships are guaranteed when a transversal cuts parallel lines, and how do we use them to find missing angle measures?

Learning Goals

  • 1State the Corresponding Angles Postulate.
  • 2Apply the Alternate Interior Angles Theorem.
  • 3Apply the Alternate Exterior Angles Theorem.
  • 4Apply the Co-Interior Angles Theorem.
  • 5Find missing angle measures using parallel line theorems.

Key Vocabulary

Corresponding Angles Postulate

If two parallel lines are cut by a transversal, then corresponding angles are congruent.

Alternate Interior Angles Theorem

If two parallel lines are cut by a transversal, then alternate interior angles are congruent.

Co-Interior Angles Theorem

If two parallel lines are cut by a transversal, then co-interior angles are supplementary.

Full lesson content coming soon

Worked examples, guided practice problems, a workbook, quiz, and downloadable PDF resources will be added to this lesson in Phase 2. The learning goals and vocabulary above reflect the complete lesson scope.